i have my root partition on btrfs and for a year and half it served me well. last week after an attempt to restore a snapper snapshot the system stopped booting, claiming:
BTRFS: error (device sda3) in __btrfs_free_extent:6944: errno=-2 no such entry
BTRFS: error (device sda3) in btrfs_run_delayed_refs:2956: errno=-2 no such entry
after some searching i ran btrfs check --repair on the partition, it fixed some errors and the system would start again. but - yesterday the error returned, same as before. so i decided to seek help of someone more knowledgeable than me.
btrfs check --repair output from the first run: https://pastebin.com/3t5EvLgA
smartctl output: https://pastebin.com/BCwJ9imU